Insulating composition, process, and article



I06. COMPOSITIONS,

COATING OR PLASTIC.

' articles having high heat resistance qualities silicamay besubstitutec may be readily made. Another object is to .electricity andwhich will stand temperapercentage of asbestos fibre forreenforcemaintain the composition in proper working this purpose isslate our having a fineness Parana "new,"was? 1,610,203

UNITED STATES PATENT OFFICE.

BRADFORD S. COVELL, 0F MERIDEN, CONNECTICUT, ASSIGNOR TO THE CONNECTICUTTELEPHONE EL CTRIC COMPANY, INCORPORATED, OF MERIIDEN, CONNECTICUT, ACORPORATION OF CONNECTICUT.

INSULATING COMPOSITION, PROCESS, AND ARTICLE.

No Drawing. Application filed August 15, 1922. Serial No. 582,076.

of say 300 mesh. Other argillaccous or 5 clayey materials such as rottenstone. talc or or re slate in One object.- of my invention is to providea composition from which cold molded w o e or in part.

The asbestos referred to is of fibrous character wit 1 t 1e fibresaveraging about 4. tures'of tqiwards of 1,000 F. without weakinch inlength the exactlength, howeveifi's ening or combustion. -Another objectis to unimportant, in fact finely ground asbestos provide a compositionand process for makmight be used as a part of the filler although ingsuch articles at a minimum of expense. in such form it has little or noreinforcing Another object is to provide a composition characteristics.which after mixing will keep in proper con- A neutral or basic saltwhich does not comdition for a considerable period of time bebine with,or absorb, water chemically, i. e.. fore molding so that substantialquantities which will not form a hydrated compound may be made up at onetime and molded as when mixed, and which will fuse below the occasionmay require. Another object is to temperature to which the piece is tobe subprovide a composition and process for makjected in use, ispreferably used. .ixamplcs ing hard refractory articles withoutrequirare sodium fluoride and sodium borate ing special heated molds orhigh fusion temborax 1. us prevents raid (WW5? perature. unmo cec powderand by fusing and com- In carrying out the invention I mix a relabiningwith other ingredients through use at tively coarse cementitiousmaterial with a high temperatures, strengthens the piece. finely dividedfiller and a binding material. A mixture of two or more salts may beused.

I also prefer to use a comparatively small As a binder I prefer toemploy waterglass in the form of sodium silicate d ssolved in water andhavmm'm proximately 1.38.

As one example of a satisfactory composition I would suggest thefollowing proportions by weight:

produce articles which are non-conductors of ment and also a fusiblesalt which tends to condition and to give added strength to the finshedarticle. This composition may be molded in suitable dies under pressureat an ordinary atmospheric temperature. The

Cement molded articles are then slowly heated to drive off moisture at amoderate temperature w i until they assume a constant Weight. F "I 4 Thecement which I prefer to use is com- P -1:/ (J f5 1 monly termed a hdraulic cement whose ina erg ass 50 u *3 8 gredients combine c emica y mthe presence of water. The most desirable grade or type of cement is onewhich is commonly known as a high temperature or refractory cement. Thebest results are obtained from the use of a comparatively coarse cement.An analysis of one satisfactory cement showed 18% would pass through ascreen having 100 meshes to the inch, 30% through an 80 mesh screen, 20%through a. 60 mesh screen, 16% through a 40 mesh screen and 6% through a20 mesh screen. It has been found that where the cement was too fine theglycerne or other lubricant. The moldin articles would crack. I

is preferably done under hi h ressure or The so-called filler performs amechanical instance, in a standard type of ton press. function offilling in the interstices of the The pressure, however, should beapplied coarser cement. The referred material for somewhat gradually andthe punch should preferably be lowered but once. I have The desiredproportions of cement and asbestos are first weighed and thoroughlymixed together in a mechanical mixer. The fusible salt and inert fillerare then added and the mixing continues. When the mass is substantiallyhomogeneous the waterglass solution is slowly added and the mixingcontinues until a uniform texture is produced.

The composition is adapted to be molded in dies such as are commonlyemployed for cold molding insulation. Preferably the punches and diesare well moistened with Examine;

found that too sudden or repeatedblows tends to cause cracks. 1

After the pieces are molded they are heated slowly so as to remove theexcess of water and baked until they assume a constant weig t. Thisheating and baking may be carr ed out in an ordinary oven. The amount.of baking and the temperature will depend somewhat upon the compositionand somewhat upon the nature, size and shape of the articles.Comparatively small articles may be heated for instance gradually fromroom tel 1mm to say 220 F. which should take about an hour. e emperaturemay then be held at approximately 220 F. for a period of another hourand the temperature then gradually raised to say 300 to 350 F. duringanother hour. The baking at this higher temperature is preferablycontinued for a period of sav another hour.

The finished pieces withstand temperatures to u wards of 2000 F. andithas been found that the strength increases with repeated heating.

Although I have mentioned a single specification for a suitablecomposition it should be understood that I consider the proportions maybe varied and that substitutions may be made. For instance. theproportion of cement may vary from to 61% of the not so important.

tomght, the filler may vary from say 41% to 15% and Himible salt may beused in larger amounts, say )0 w ien greater strength is desired andgood appearance is Generally speaking the total of the other ingredientsshould remain approximately as above indicated but with a largerpercentage of cement the waterglass solution may be somewhat increased.I also consider that the percentage of asbestos may be increased in somecases. Where it is not necessary to keep the composition in its un-.molded state for any length of time the percentage of fusible salt maybe decreased. The powder will keep almost indefinitely in a desiccatorwhere the humidity is controlled.

I claim:

1. A cold moldable composition comprising cement 35 to 61%, slateiioilr41 to 15%, and waterglagggolution approximately 18%.

2. A cold moldable composition comprising approximately 50% of cementand asbestos. and 50% of slate flour. a fusible salt and a liquidbinder.

3. A cold I oldable composition compris ing cement approximately 48%,asbestos and slate flour approximately 30%,and a fuslble draulic cement,approximately 30 parts of slate flour and asbestos, and approximately 20parts of a water solution containing waterglass.

6. A moldable insulating composition comprising approximately 48 partsof a coarse highly refractory hydraulic cement, approximately 30 partsof a very fine inert filler all mixed with approximately 20 parts of awater solution, and which at normal pressure and temperature is slowdrying andnonsetting but which when highly compressed and slowly bakedhardens and assumes a constant weight.

7. A cold moldable composition comprising a mixture of approximately 48%of high temperature hydraulic cement, approximately 30% of slate flourand other inert material. approximately 4% of a non-hygroscopic fusiblesalt, and approximately 18% of a water solution.

8. A cold moldable composition comprising coarse high temperatureresisting hydraulic cement. slate flour. waterglass solu-' tion ofapproximately 1.38 specific gravity,

a small percentage of asbestos, and suflicient' non-hygroscopic fusiblesalt to prevent rapid setting under normal atmospheric conditions.

'9. An article of manufacture 'icomposedof a high temperature hydrauliccement, as bestos fibre. slate flour. a fusiblesalt and-a binder. andhaving the qualities of withstanding high temperature without weaken-=ing. and a non-conductor of electricity.

10. An article of manufacture comprising .35 to 61% of a highlyrefractory hydraulic cement, 43 to 17% of slate flour and asbestos. upto 8% of sodium fluoride and some sodium silicate, said article being agood elec-l trical insulator. heat resisting, hard, and of constant weiht. I v

11. A article of manufacture comprising a cold molded composition ofapproximately 50% of a coarse hydraulic cement. approximately 30% of avery fine inert filler and a small percent of a basic salt fusedtherewith. and having qualities of electrical insulation, heat resistinand constant weight.

. BRADFORD soovELL,

